1. Field
This disclosure relates to small molecule drugs typified by a bicyclic aliphatic group. The disclosed compounds include analgesic compounds and antipyretic compounds. Also disclosed are methods of synthesis, drug combinations, and medical uses.
2. Description
Nonsteroidal anti-inflammatory compounds, or NSAIDs, are an extremely useful group of small molecule drugs, typified by acetylsalicylic acid, ibuprofen, and naproxen. These are often sold without prescription, and are variously used to treat pain, inflammation, and fever. However, NSAIDs can have undesirable side effects, including gastric upset or gastric bleeding.
Acetaminophen, also known as paracetamol or APAP, is also an effective pain reliever often sold over the counter (without prescription). Although it shares analgesic and antipyretic properties with NSAIDs, it has only weak anti-inflammatory properties, and is thus not an NSAID. Unlike many NSAIDs, acetaminophen does not cause gastric upset or bleeding in prescribed doses. Thus, it is an extremely useful drug for those wishing analgesia without adverse gastric side effects.
Acetaminophen is often combined with other drugs for relief of symptoms of influenza and the common cold, among other indications. It is particularly useful in combination with opioid analgesics, where it exhibits synergistic analgesic properties and allows patients to achieve adequate pain relief with lower doses of opioids. The most widely prescribed drug in the United States is a combination of acetaminophen and hydrocodone, with over 130 million prescriptions in the year 2010. Other acetaminophen-opioid combinations, including combinations with oxycodone, are also widely prescribed.
Acetaminophen poisoning is the most common cause of acute liver failure in the Western world, and acetaminophen accounts for the most drug overdoses in the English-speaking world. Acetaminophen is metabolized to form N-acetyl-p-benzoquinoneimine (NAPQI), which depletes glutathione in the liver and injures hepatocytes, leading to acute liver failure and often death. The acetaminophen-opioid combination drugs are commonly implicated in such toxicity, for various reasons. First, patients might not recognize that the prescribed pain relievers contain acetaminophen, and may supplement with acetaminophen if pain relief is inadequate. Second, continued administration of opioids can lead to tolerance and the need for increased dosages to obtain a comparable opioid effect, and users or abusers of the combination drugs may exceed safe dosages of acetaminophen as a consequence.
This has led the U.S. FDA to seek reduced amounts of acetaminophen in the opioid combination drugs and has also led an FDA advisory panel to recommend banning such drugs all together. Although the acetaminophen-opioid drugs remain on the market, there is a strong need for a less toxic replacement without the same hepatotoxicity risks.
Acetaminophen has the structure:

Acetaminophen is metabolized in vivo to form the hepatotoxic compound N-acetyl-p-benzoquinoneimine:
